Mound Excavation

Rock Lines

Two rock lines dating back about 2,300 years. These mark the June solstice sunset.

Peruvian Rock Lines

Credit: Charles Stanish

A distant look at the two solstice-marking lines, with a person for scale.

Solstice Lines

Credit: Charles Stanish

A view of two rock lines that mark the June solstice with a person for scale.

Day Before Solstice

Credit: Charles Stanish

Two student archaeologists atop the Chinca Valley Mono B mound on June 20, 2013, the day before the winter solstice. On the solstice day, the sun would fall on the heads of those on the mound when viewed from behind the structure, archaeologist Charles Stanish of UCLA told Live Science. The mound was intentionally built for this effect, Stanish said.

Mound Before Solstice

Credit: Charles Stanish

Mono B on the day before solstice (June 20) in 2013. A marker points to the solstice sunset.

Solstice Mound

Credit: Charles Stanish

The Mono B mound before solstice, with annotations explaining how this astronimcal marker functioned.

Author Bio

Stephanie Pappas, Live Science Contributor

Stephanie interned as a science writer at Stanford University Medical School, and also interned at ScienceNow magazine and the Santa Cruz Sentinel. She has a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science writing from the University of California, Santa Cruz.

Mound Excavation

Rock Lines

Two rock lines dating back about 2,300 years. These mark the June solstice sunset.

Peruvian Rock Lines

Credit: Charles Stanish

A distant look at the two solstice-marking lines, with a person for scale.

Solstice Lines

Credit: Charles Stanish

A view of two rock lines that mark the June solstice with a person for scale.

Day Before Solstice

Credit: Charles Stanish

Two student archaeologists atop the Chinca Valley Mono B mound on June 20, 2013, the day before the winter solstice. On the solstice day, the sun would fall on the heads of those on the mound when viewed from behind the structure, archaeologist Charles Stanish of UCLA told Live Science. The mound was intentionally built for this effect, Stanish said.

Mound Before Solstice

Credit: Charles Stanish

Mono B on the day before solstice (June 20) in 2013. A marker points to the solstice sunset.

Solstice Mound

Credit: Charles Stanish

The Mono B mound before solstice, with annotations explaining how this astronimcal marker functioned.